She only drives in reverse....but, only if I put her in fifth gear...while in 4WD.

Any ideas? It literally happened out of nowhere....I made a trash run one day, and a mile away from the house she just stopped moving forward while in gear. And the only gear that works is fifth...but in 4WD...and instead of forward, she goes backwards.

Yes, I've got all gears....can put it in gear. It's just that none of the gears engage. I can go 4 low and 4 high. None of the gears engage...except fifth, in 4-Hi, and when I can get it there....it goes backwards.

When it will move in 4Hi, is the rear driveshaft getting power? Are the hubs locked in to allow the front axle powering the vehicle? Only moving in 4x4 (with front hubs locked in) usually makes think a spun hub/broken shaft on a 2 piece axle. Also, pull the top cover off the transmission and check the shift forks and inside of the transmission.

Reverse in 5th gear sounds like shift forks to me, but that doesn't explain it only working if 4Hi. So then I thought a body lift shifted messing with stuff, but you don't list one in your profile. So now I'm wondering if your body mounts are shot and your tub shifted on the frame?

In reality, I think you've got more than one problem, and for some stupid unexplainable reason they all showed up at once....